You can add any Mastodon server as a Web panel. That works just fine. That is really how we integrated Vivaldi Social.
I think the question of tabs is the same as for any feature really. We have the principle that we adapt to your needs. Thus we have the ability to have the tabs on the left, right, top or bottom or even hidden. Similarly we have 3 different tab stack methods and generally just a lot of settings. This comes at a cost, but we think that is how we should do things. Thus we adapt to your requirements and needs. The others just do not think that way.